THE VARIATION OF ATOMIC PROPERTIES Charina Cameron Jenn Lau Stephanie Coldwell Lyndsay Vidito

Atomic Radius The size of the atom.

First Ionization Energy First ionization energy is the energy required to remove an electron from an atom. NOTE: Electronegativity is "...the ability of an atom in a molecule to attract shared electrons to itself." (Zumdahl, 1995, Chemical Principles, p. 571)

PROCEDURE "A" QUESTIONS 1) How does the portion of the graph for elements 3 to 10 compare with the portion of the graph for elements 11 to 18? The pattern is the same. The trend is that you are always starting at a peak and then diminishing in radius inversely. The portion from 11 to 18 is higher up in atomic radius but follows the same trend in decreasing in atomic radius as the atomic number increases.

PROCEDURE "A" QUESTIONS 2) How does the portion of the graph for elements 19 to 36 compare with the portion of the graph for elements 11 to 18? There are approximately twice as many elements and the comparison is between the third and forth period elements. The expected peak (if the pattern repeated) at element 25 or 26 does not occur because this is the middle of the transition elements. Elements in the middle of a period have a smaller atomic radius than the ones at the beginning (group IA).

PROCEDURE "A" QUESTIONS 3) If the data for the transition metals were missing and the data for elements 20 and 31 were joined directly with a broken line, how would the portion of the graph for elements 19 to 36 then compare with the portion of the graph for elements 11 to 18? removed The portions would be almost identical but the atomic radius numbers would be higher so the curve would be shifted higher. The transition elements are numerous and have smaller atomic radius than the Alkali metals.

PROCEDURE "A" QUESTIONS 4) If there is a periodic variation (i.e., regular repetition) between atomic radii and atomic numbers of the elements, how would you describe it? For any period, the atomic radius is highest for its alkali metal and decreases gradually until it is smallest for the noble gas in that period. Also, as you go down a group, the atomic radius increases.

PROCEDURE "A" QUESTIONS 5) How does the portion of the graph for elements 3 to 10 compare with the portion of the graph for elements 11 to 18? The pattern is the same, but the overall trend is slightly lower. This means that less ionization energy is needed to remove the valence electrons from the elements of period three than from period two. The trend is that more ionization energy is required to remove valence electrons from the noble gases than from the elements in the beginning of the rows. This is why noble gases are so inert.

PROCEDURE "A" QUESTIONS 6) How does the portion of the graph for elements 19 to 36 compare with the portion of the graph for elements 11 to 18? Overall the ionization energies are lower. They are highest for the inert gases and lowest for the left side of the periods. However, from 19 to 36, 10 transition elements are inserted which extend the flat part of the curve in the middle of the period where ionization energies are lower.

PROCEDURE "A" QUESTIONS 7) If the data for the transition metals were missing and the data for elements 20 and 31 were joined directly with a broken line, how would the portion of the graph for elements 19 to 36 then compare with the portion of the graph for elements 11 to 18? The portions remaining would be almost identical but the ionization energies would be shifted to lower levels. Groups IIIA to VIIIA would have a similar ionization energy pattern. The transition elements inserted between groups IIA and IIIA are numerous (10) and have lower ionization energies so they flatten and lengthen the curve. removed

PROCEDURE "A" QUESTIONS 8) If there is a periodic variation between first ionization energy and atomic numbers of the elements, how would you describe it? For any period, the first ionization energy is highest for the noble gas (Group VIIIA) and lowest for the alkali metals (Group IA). The ionization energy then increases from the alkali metals to the noble gases in a period.

CONCLUDING QUESTIONS: 1) What do you estimate to be the missing value of the atomic radius of manganese? Of selenium? We estimated that the atomic radius of manganese was about 0.12 nm. On the Alchem periodic table of the elements, the atomic radius is given as 0.140 nm. For selenium, we estimated the atomic radius to be 0.115 nm which is the same as what is given on the periodic table.

CONCLUDING QUESTIONS: 2) What do you estimate to be the missing value for the first ionization energy of manganese? Of selenium? We estimated that the first ionization energy of manganese was about 750 kJ/mol of atoms. For selenium, we estimated the first ionization energy to be about 1100 kJ/mol of atoms.

CONCLUDING QUESTIONS: 3) Would you expect the atomic radius to be larger or smaller for element 37 than for element 36? Give the reason for your answer. We would expect that the atomic radius for element 37 to be larger than that of element 36. The trend is for the elements at the beginning of the period (Alkali metals, such as Rb) to have bigger atomic radii than the elements at the end (e.g., Kr). Therefore, the atomic radii diminish as one goes to the right in the periodic table.

CONCLUDING QUESTIONS: 4) What should be the approximate value for the first ionization energy of element 37? We would expect that the first ionization energy should be about 400 kJ/mol of atoms for element 37. The trend is for the elements at the beginning of the period (Alkali metals, such as Rb) to have lower first ionization energies than the elements at the end (e.g., Kr). Therefore, the first ionization energy increases as one goes to the right in the periodic table.

CONCLUDING QUESTIONS: 5) Which one of all the elements whose atomic numbers are larger than 36 should have the largest first ionization energy, and what will be the approximate value of its first ionization energy? We would expect that the noble gases would have the highest values for the first ionization energies. Of the two inert gases above element 36, we would expect xenon to have a higher value because the first ionization energy appears to decrease as you go down a group. Since element 36 has a value of 1351 kJ/mol of atoms, we would expect element 54 to have a value of about 200 less. We predict a value around 1150 kJ/mol of atoms for this element's first ionization energy.

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